Ma Wenfang, Li Baiyun, Zheng Litong, Peng Yunjing, Tian Rui, Yuan Yangyang, Zhu Lingcheng, Su Jing, Ma Fengwang, Li Mingjun, Ma Baiquan
State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China.
Foods. 2021 Sep 16;10(9):2198. doi: 10.3390/foods10092198.
Organic acids and soluble sugars are the major determinants of fruit organoleptic quality. Additionally, DNA methylation has crucial regulatory effects on various processes. However, the epigenetic modifications in the regulation of organic acid and soluble sugar accumulation in apple fruits remain uncharacterized. In this study, DNA methylation and the transcriptome were compared between 'Honeycrisp' and 'Qinguan' mature fruits, which differ significantly regarding soluble sugar and organic acid contents. In both 'Honeycrisp' and 'Qinguan' mature fruits, the CG context had the highest level of DNA methylation, and then CHG and CHH contexts. The number and distribution of differentially methylated regions (DMRs) varied among genic regions and transposable elements. The DNA methylation levels in all three contexts in the DMRs were significantly higher in 'Honeycrisp' mature fruits than in 'Qinguan' mature fruits. A combined methylation and transcriptome analysis revealed a negative correlation between methylation levels and gene expression in DMRs in promoters and gene bodies in the CG and CHG contexts and in gene bodies in the CHH context. Two candidate genes ( and ), which encode tonoplast-localized proteins, potentially associated with fruit soluble sugar contents and acidity were identified based on expression and DNA methylation levels. Overexpression of in tomato increased the fruit soluble sugar content. Moreover, transient expression of in tobacco leaves significantly decreased the pH value. Our results reflect the diversity in epigenetic modifications influencing gene expression and will facilitate further elucidating the complex mechanism underlying fruit soluble sugar and organic acid accumulation.
有机酸和可溶性糖是果实感官品质的主要决定因素。此外，DNA甲基化对各种过程具有关键的调控作用。然而，苹果果实中有机酸和可溶性糖积累调控中的表观遗传修饰仍未得到表征。在本研究中，比较了‘蜜脆’和‘秦冠’成熟果实的DNA甲基化和转录组，这两个品种在可溶性糖和有机酸含量方面存在显著差异。在‘蜜脆’和‘秦冠’成熟果实中，CG背景下的DNA甲基化水平最高，其次是CHG和CHH背景。差异甲基化区域（DMR）的数量和分布在基因区域和转座元件之间有所不同。‘蜜脆’成熟果实中DMRs所有三种背景下的DNA甲基化水平均显著高于‘秦冠’成熟果实。甲基化和转录组联合分析显示，在CG和CHG背景的启动子和基因体以及CHH背景的基因体中，DMRs的甲基化水平与基因表达之间呈负相关。基于表达和DNA甲基化水平，鉴定出两个候选基因（和），它们编码液泡膜定位蛋白，可能与果实可溶性糖含量和酸度有关。在番茄中过表达增加了果实可溶性糖含量。此外，在烟草叶片中瞬时表达显著降低了pH值。我们的结果反映了影响基因表达的表观遗传修饰的多样性，并将有助于进一步阐明果实可溶性糖和有机酸积累的复杂机制。
